The proposed research involves the design, synthesis, characterization and biological testing of new types of biological materials with a view to prosthetic implantation. The materials are of two types: 1) synthetic copolypeptides, and 2) chemically modified tissue of which elastin and collagen are major components. Preliminary evaluation with both types of material indicates superior performance in the biological milieu. Subsections of this proposal are concerned with characterization of the materials by x-ray diffraction, electron microscopy and various forms of spectroscopy; evaluation of nature and performance of the surface including attempt to identify interaction with plasma proteins and platelets; mechanical testing and prosthetic fabrication; and prosthetic testing "in vivo" and "in vitro" to evaluate compatibility (toxic and immune responses, degradation, rejection (if any) and thrombogenicity). A major objective of this proposal is to understand the factors underlying the biocompatibility of biological materials by a detailed systematic approach involving both basic and applied research.